RFR: 8342818: Implement CPU Time Profiling for JFR

[Johannes Bechberger]

On Sat, 21 Sep 2024 11:30:10 GMT, Erik Gahlin <egahlin at openjdk.org> wrote:

>> Indeed. This is important for getting the correct distribution. Since we are sampling per thread cpu time, having one global 'event loss' is suboptimal as it is not possible to easily assign the lost events to threads proportionally.
>> But because keeping the event loss per thread would be too expensive we settled for this solution. OTOH, for unwalkable samples we can 'cheaply' record them and maintain the distribution.
>
> Could we add a field, i.e. "failed" and "Failed Stack Walk", to indicate failure instead of using null, which could be because stack trace has been disabled.

That's a good idea. So a failed sample would have `failed=true,stackTrace=null`?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/20752#discussion_r1769548474